1. Field of the Invention
This invention pertains to the alignment of the phases of error signals from two orthogonal axes, such as the elevation and azimuth axes, in a monopulse antenna tracking system such as used in a satellite tracking antenna.
2. Description of the Prior Art
A prior art search was performed and uncovered the following U.S. patent references:
U.S. Pat. Nos. 3,842,420 and 4,030,099 describe an antenna tracking technique called "step track" which involves stepping the direction of an antenna in a manner which increases the strength of the received signal. My invention is concerned with optimizing an entirely different tracking technique known as "monopulse" tracking, wherein antenna receive elements develope two error channels corresponding to tracking errors with respect to two orthogonal axes. The cited patents also make no mention of a simulated far field source or a completely automatic means of aligning the phases of the signals within the system, as in my invention.
U.S. Pat. No. 3,582,950 describes an antenna feed system which generates elevation and azimuth error channels needed for monopulse tracking. The necessity of receiver alignment phase shifters is recognized; however, no mention is made of a simulated far field source, near field compensation phase shifters, or an automatic means of phase aligning the system, as in my invention.
U.S. Pat. No. 3,821,741 describes an antenna feed system which provides elevation and azimuth error channels needed for monopulse tracking. Phase shifters are included in the feed to compensate for phase shifts introduced by the feed; however, no means is shown to compensate for phase shifts introduced by the receivers or other portions of the system. No mention is made of a simulated far field source, or an automatic means of phase aligning the entire system, as in my invention.